Choosing The Right Size Of Tankless Water Heater

Professional water heater installation and repair for Dripping Springs homes

You’ve made the wise decision to upgrade to a tankless water heater. A tankless water heater has the ability to bring many benefits to your home. Now, the next step is crucial: selecting the right size and type of tankless water heater to meet your specific needs. 

In this guide, we’ll explore the key factors to consider when choosing the perfect electric tankless water heater for your home.

Sizing Matters

One of the fundamental aspects of selecting the right tankless water heater is getting the size right. A unit that’s too small won’t meet your hot water demands, while one that’s too large can be an unnecessary expense. 

How do you determine the correct size for your home?

1. Flow Rate

The flow rate is the hot water your household uses at a given time. To calculate it, list the appliances and fixtures that require hot water simultaneously. These may include showers, dishwashers, washing machines and sinks. 

Each has a flow rate, typically measured in gallons per minute (GPM). Sum up the GPM values of all these appliances and fixtures to find the total flow rate your tankless water heater needs to handle. 

For example, if your shower uses 2 GPM and your dishwasher uses 1.5 GPM, your desired water heater should have a minimum flow rate of 3.5 GPM to meet these simultaneous demands.

2. Temperature Rise

The temperature rise refers to the difference between the incoming cold water temperature and the desired hot water temperature. In colder climates, the temperature rise will be more significant. To determine the required temperature rise, determine the average incoming water temperature in your area and subtract it from your desired hot water temperature.

For instance, if your incoming water temperature is 50°F and you want your hot water to be at 120°F, your temperature rise is 70°F. Your water heater should be capable of achieving this temperature rise for your desired flow rate.

3. Sizing Guidelines

Most tankless water heater manufacturers provide sizing guidelines for flow rate and temperature rise. These guidelines help you select the right unit for your needs. 

It’s essential to consult these guidelines or speak with a professional to ensure you make the correct choice.

Other Important Pointers To Consider Before Buying A Water Heater

1. Consider Energy Efficiency

When selecting a water heater, it’s crucial to consider energy efficiency. Look for units that have a high Energy Factor (EF) rating. 

This rating indicates how efficiently the unit converts energy into hot water. The higher the EF rating, the more energy-efficient the water heater.

2. Maintenance and Longevity

While tankless water heaters are generally low-maintenance, it’s still important to schedule regular check-ups to ensure longevity and performance. 

Regular maintenance can prevent scaling and other issues that reduce efficiency over time. Be sure to inquire about maintenance plans from your installation provider.

3. Environmental Impact

As mentioned in our previous guide, “Improve Your Quality Of Life With A Tankless Water Heater” tankless water heaters contribute to a reduced environmental impact due to their energy efficiency. They consume less energy, which leads to lower greenhouse gas emissions, helping to combat climate change. 

By choosing a tankless water heater, you’re not only improving your quality of life but also making an eco-conscious decision.

4. Expert Installation Matters

Choosing the right size and type of water heater is the first step. Equally important is a professional installation. An experienced technician will ensure that your unit is correctly sized, correctly installed and performs at its best. 

Improper tankless water heater installation can lead to performance issues and potentially negate the energy-saving benefits of a water heater.


Choosing the right size and type of tankless water heater for your home is a decision that can significantly enhance your quality of life. By considering factors like flow rate, temperature rise and the type of unit that fits your needs, you can always have a continuous hot water flow, save on energy bills and reduce your environmental impact. A professional water heater installation will ensure to effectively heat water with no concern of running out of hot water.

Additionally, consulting with professionals like Lone Star Water Services ensures you make the most informed choice and receive top-notch installation, repair and maintenance services. Don’t hesitate to upgrade to a tankless water heater and experience the convenience, cost savings and eco-friendly benefits it brings to your home. Visit us today.

Make the smart choice today and enjoy a more comfortable and energy-efficient way of enjoying hot water. Your home and your wallet will thank you for it.

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